The present invention relates generally to power cutting devices and particularly to a feed mechanism for assisting in application of a feed force for a cutting device.
Hand operated chain saws are used in a variety of applications from wood cutting to aggregate cutting. To cut a workpiece, the operator must move the guide bar through the workpiece by urging the moving saw chain against the workpiece. Bucking teeth affixed to the chain saw body and protruding toward the workpiece previously have assisted in providing such a feed force, i.e., the force of the saw chain against the workpiece to accomplish cutting. The bucking teeth engage the workpiece adjacent the kerf as a pivot point for rocking the chain saw body and moving the saw chain within the workpiece with the aid of leverage. Although the mechanical advantage provided by bucking teeth aids in providing a feed force, in many cases, due to the magnitude of cutting forces required or necessary orientation of the chain saw, the operator may have difficulty. This is especially true during extended periods of use where large magnitude cutting forces or difficult saw orientation is required.
In certain applications the combined weight of the chain saw and the force needed to urge the saw chain through the workpiece can be burdensome. For example in aggregate cutting, the chain saw weight can exceed 30 pounds and the required feed force may be as much as 70 pounds. For up-cuts the operator must not only carry the weight of the chain saw, but also the required feed force for a total operator applied force exceeding 100 pounds. For horizontal cuts the operator may have difficulty maintaining a desired horizontal orientation, as by vertically supporting the chain saw, while applying the necessary feed force, as by pushing the saw in a horizontal plane and parallel to the line of cut.
Another problem encountered in aggregate cutting is use of bucking teeth for engagement of the aggregate material. When applied to softer material, e.g., wood products, bucking teeth are well adapted for secure engagement since they dig into the product surface. Aggregate material, however, presents a much harder and less resilient workpiece and requires a substantially greater magnitude feed force. Bucking teeth either cannot penetrate or may tend to crumble the aggregate material upon engagement and provide a less secure purchase. As conventionally applied to aggregate material, bucking teeth need be extremely hard and sharp, an expensive requirement, to obtain any significant engagement of the workpiece as a leverage point.
Accordingly, a chain saw would desirably include a mechanism to aid the operator in engaging the workpiece and developing the necessary feed force, especially where large magnitude feed force is required or difficult saw orientation is necessary.